feat(3p/lisp/mime4cl): cache offset in delimited-input-stream r/3749

By computing the amount the stream position advanced we can save a
syscall on every read which speeds up mime:mime-body-stream by /a lot/,
e.g. extracting a ~3MB attachment drops from over 15s to under ~0.5s.
There's still a lot to be gained and correctness left to be desired
which can be addressed as described in the newly added comment.

Change-Id: I5e1dfd213aac41203f271cf220db456dfb95a02b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5073
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

0 files changed, 0 insertions, 0 deletions